Terminal block for current transformers



Dec. 30, 1930. J. B. GIBBS 1,786,746

TERMINAL BLOCK FOR CURRENT TRANSFQRMERS Filed Jan. 18, 1929 2Sheets-Sheet 1 I 6 l8 19 e3 0 24 7 I7 P: )5 '5: 1 1, 11 H ll l3 l4 l8INVENTOR 25565. Gibbs.

ATTORNEY Dec. 30, 1930. J. B. GIBBS TERMINAL BLOCK FOR CURRENTTRANSFORMERS Filed Jan.

2 Sheets-Sheet 2 INVENTOR J'esseB Gibbs.

AT'TORNEY short circuiting switch, that is normally Patented Dec. 30,1930 UNITED STATES,

JESSE B. GIBBS, 0F SHARON, rENNsYLvANIA, ASSiGNOR ro WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION or P NN Y VANI TERMINAL{BLOCK r03 oUNRE'Nr'rn NsroRNERs Application filed- January 18,1929.Serial N 333,386.

My invention relates to current transformers, and particularlytoterminal blocks therefor that are provided with means for short.circuitingthe secondary winding of I the current transformer.

.It is desirablethatthe secondary winding of a current transformerbemaintained short circuitedwhen it is not connected to a load circuit,since, when the secondary winding of the transformer is open-circuited,the impedanceof, the primary circuit may be large and the voltage of thesecondary circuit so, vhigh as to damage the insulation of thetransformer or cause injury to persons-con- 'zoithe terminals, in orderthat the load circuit may-function properly,

My invention contemplates the provision of a terminal block for currenttransformers comprising a base for supporting terminals for thesecondary winding thereof and a biased to a circuit-closing position,for con necting the secondary terminals of the transformertogether, andwith a cover for the two positions, and, when attached in one of itspositions, causes the switch contacts to become disengaged, while, whenattached in the other position, permits the switch contact -membertoremain in i engagement.

The cover isprovided, in one side, with.

as toexpose them when the coveris attached y or outof view ofthe-operator, and the side of to the base in a position to'open-theshort circuiting switch, thus permitting'the load- I circuitconductors to -pass through the-cover.

mitting the short-circuiting switch. to remain closed, the openingsinzthe slide of the cover are on the back of the terminal block,

the cover then in; view completely seals the terminals, The. position ofthe cover of the terminal block. upon the *base," therefore,

nectinginst'ruments to the secondary circuit basewhichmay be attached toit inone of serves as a visual indication of whether theshort-circuiting switch is in its openposition ,circuiting switchfor thesecondary circuit of the transformer. i

A second object of my invention is to so construct the cover ofthe-terminal block that it may also serve as a visual lndicating meansfor showing whether the short-circuiting switch is-in its circult-opemngor circuit-closing-position.

My inventionwill be better understood by reference to the accompanyingdrawings, wherein Figure, 1 is a perspective view of a currenttransformer provided with a terminal block constructed in accordancewith my invention,

Fig. 2 is a transverse sectionalviewof one I preferred form of terminalblock taken along the lines II II of Fig. 3, A Fig. 3 is a verticalsectional view of the form of the embodiment of the invention shown inFig. 2 and is taken on the line IIIIII of Fig. 2, I

Fig. 4 is a transverse sectional view of asecond preferred form oftheinvention,

taken along the line IVIV of Fig. 5, V

Fig. 5 is a verticalsectional view, taken along the line V.V of Fig. 4,1 Fig. 6 is a perspective viewv of the terminal block with the coverplaced thereon in aposition to expose the secondary terminals of thetransformer, and ,1 V

- Fig. 7 is a perspective viewof a terminal block with the cover placedthereon in a po- 'sition to conceal the secondary terminals of thetransformer. When the cover is attached ina-position per- Referring tothe drawing, a terminal block l-is provided in any suitablelocation-with respectto a current transformer 2, and, as

illustrated in Fig. 1 of'the' drawing, may be mounted on the ironlaminated structure" forming the magnetic circuit of the transformer.

held tightly in place thereon by means of the spring clips 6 and 7 whichmay be arranged to fit into grooves in the ends of the terminal blockand cover and are provided with bent end portions for gripping the topof the cover, as shown in the several figures of the drawing. The covermay be removed from the base of the terminal block by lifting itupwardly, thus causing the upper ends of the spring clips 6 and 7 toseparate suilicient- 1y to permit the cover to pass between them.

11 case it is desired to lock the cover member upon the base so that itwill not be tampered with by unauthorized persons, a sealing wire 8 maybe passed through small openings in the ends of the spring clips, asshown in Fig. 3, and fastened with a seal, thus pre venting the clipsfrom separating.

The terminal block base 4 may be attached to any suitable supportingmember by bolts 11 and 12 which also serve to tightly hold the lowerends of the spring clips 6 and 7 in place. Terminal studs 13 and 14 maybe provided in the base of the terminal'block,

' and connected to the ends of the secondary conductors of thetransformer, as by the nuts and set screws 15 and 16. Each stud also maybe provided with nut 17, washer 18, and lock nut 19 for receiving andholding the conductors of a load circuit, such as a relay, or thecurrent coils of indicating instruments.

r The cover member is provided with two openings 21 and 22, as shown inFigs. 2, 4 and 6 of the drawing, and may be placed upon the base portionof the terminal block in either of the two positions shown in Figs. 6and 7, respectively.

In the position shown in Fig. 6, the openings 21 and 22 are sopositioned as to expose the terminal studs 13 and 14 and permit theleads of the load circuit to pass through these openings.

In the position shown in Fig. 7, the openings are positioned on thereverse side of the terminal block, next to the transformer windings,and the solid wall of the cover conceals the studs 13 and14 from view.

The position of the cover shown in Fig. 6 of the drawing is that usedwhen a load circuit is connected to the secondary terminals of thetransformer and the short-circuiting switch is in its open-circuitposition, and the position of the cover shown in Fig. 7 is that usedwhen the load circuit is not in use, and the secondary circuit of thetrans former is short 'circuited.

In the form of the invention shown in Figs. 2 and 3 of the drawing, ashort-circuiting switch is provided comprising two wing switch blades23' and 24. The blades are connected, respectively, to the studs 13 and14 to normally engage each other, thus closmg a circuit between theterminals 13 and 14. It will be noted by reference to the drawing, thatthe spring blades 23 and 24 of the switch are of such width that theyoccupy less than one half of the space between the side walls of thecover, and that a rib 25 is formed on one side of the cover member toextend slightly less than one half of the distance between the sidewalls thereof.

In the position of the cover shown in Figs. 2 and 3, the rib 25 isbeside the spring blades but not in engagement therewith. If the coveris removed and the ends thereof reversed, and the cover again replaced,the rib 25, which will be on the same side of the block as the springblades 23 and 24 and will pass between and separate them, as the coveris pushed downwardly between the spring clips 6 and 7, thus opening theshort circuit between the terminals 13 and 14. This position of the rib25 is shown in dotted lines in Fig. 3. v

lVith the form of terminal block and shortcircuiting switch illustratedin Figs. and 5 of the drawing, a spring contactor or switch blade 26,having an upturned hump portion 27, is connected to one of the terminalstuds 18, and is normally biased upwardly against a cont'actor blade 28,which is connected to the other terminal stud 14. A rib 29 is shownwhich, when the cover is in the position illustrated in Figs. 4 and 5,does not interfere with the engagement of the switch blades 26 and 28. vhen, however, the cover is removed and is replaced withthe ends thereofreversed, the rib 29 will be in the position shown in dotted lines inFig. 5 and will engage the upturned or hump portion 27 of the blade 26,thus forcing it downwardly and out of engagement with the blade 28. Theblock base and cover members may be made of suitable molded compositionof insulating material.

It will be observed from the above description of the two embodiments ofmy invention that, when the terminal block'cover is placed upon the basein the normal position for use, an accidental short circuit of thesecondary terminals on the block, which would prevent the instrumentsfrom indicating, cannot be made, and that when the cover is removed fromthe base, or when it is replaced in the other of its two positions, thesecondary ter minals of the transformer will remain shortcircuited, thuspreventing injury to the transformer windings or to the operator.

Since many modifications may be made in the details of the structuresdisclosed to illustrate embodiments of my invention without departingfrom the spirit thereof, I do not wish to be limited otherwise than bythe scope of the appended claims.

I claim as my invention:

1. A current-transformer terminal block comprising a base, secondaryterminals and a spring-closed contact switch mounted on the base forshort-circuiting said terminals, and a cover formed to be secured uponsaid base in either of two positions, said spring-closed contact switchbeing arranged to be automatically opened when said cover is positionedupon said base in one of its said two positions.

2. A current-transformer terminal block comprising a base, secondaryterminals, and a spring-closed contact switch mounted on the base forshort circuiting said terminals, a

cover formed to be secured upon said base in either of two positions,and means attached to said cover for actuating said switch to itsopen-circuit position when said cover is positioned upon said base inone of its said two positions, v

3. A current-transformer terminal block comprising a base, secondaryterminals, and a spring-closed contact switch mounted on the base forshort circuiting said terminals,

and a cover formed to be secured upon said base in either of twopositions, a rib on said cover so positioned with respect to said switchas to actuate the switch to a circuit-opening position when the cover ispositioned upon said base in one of its said two positions but not toactuate the switch when the cover is positioned upon said base in theother of its said two positions.

4. A current-transformer terminal blockcomprising a base, secondaryterminals-and a spring-closed contact switch mounted on the base forshort circuiting said terminals, and a cover formed to be secured uponsaid base 1n either of two positions, a r1b on said cover so positionedwith respect to said switch as to actuate the switch to acircuit-opening position when the cover is positioned upon said base inone of its said two positions but not to actuate the switch when thecover is positioned upon said base in the other of its said twopositions, and visual means whereby the position of the short circuitingswitch may be 1(:iloserved from the position'of the cover memer. 1 1

5. A current-transformer terminal block comprising a base, secondaryterminals and a switch mounted on the base for short circuit ing saidterminals, said switch being normally biased to its circuit-closingposition, and a cover formed to be secured upon said base in either oftwo posltlons, said cover being so shaped as to conceal said terminalsin one of its positions and to expose said terini- I nals 1n the otherof its posltlons, and means for automatically actuating said switch toits circuit-opening position when the cover is secured upon said base ina position to expose said terminals.

In testimony whereof, I have hereunto subscribed my name this 9th day ofJanuary,

JESSE B. GIBBS.

